There are several implementations of Java. The three most common implementations when talking about it for Ubuntu are:

OpenJDK: The primary goal of the OpenJDK project is to produce an
open-source implementation of the Java SE Platform (6 and 7). This is
the default version of Java that Ubuntu uses and is the easiest to
install.

Sun Java: Sun Java is the reference implementation for Java 6. Its support has been discontinued in Ubuntu.

Oracle Java: Oracle Java is the OpenJDK Java Se Platform version 7 implementation from Oracle. Oracle introduced with this implementation a license that prevents distribution.

Since Ubuntu 11.10 (Oneiric Ocelot) and due to license issues Ubuntu will no longer distribute Oracle's JDK and JRE. Also, previous versions supplied on PPAs suffer from security issues and are not recommended to be installed on any Ubuntu system.

There are no more supported .deb releases from Ubuntu with reference to Sun Java or Oracle Java, Ubuntu officially supports OpenJDK and OpenJRE implementation of Java which is the base for Oracle's own implementation.

OpenJRE is the official implementation of Java Runtime Environment (JRE) for your Ubuntu systems and should suffice to run any Java program that you might require and it's included in the main repository and it's easily installable.

OpenJRE

Or by opening a terminal and typing

sudo apt-get install openjdk-7-jre

The openjdk-7-jre package contains just the Java Runtime Environment. If you want to develop Java programs then install the openjdk-7-jdk package:

Also important is to install the wrapper for supporting Java applications on your web browser, the Iced-Tea Java Plugin.

IcedTea Plugin

Or via a terminal

sudo apt-get install icedtea-plugin

Or look for icedtea-plugin in the Ubuntu Software Center.

To make sure that you are running the correct version of Java, use this command to set your choice:

Under 15.04 the icedtea-7-plugin does not work well with Firefox. I've found that downloading a tar.gz distribution and manually symlinking libnpjp2.so into /usr/lib/firefox-addons/plugins made it work. Note that the websites need to be marked as trusted too in the java control panel (this in turn is only possible if you do not have spaces in the full folder name of the unpacked jre).
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Thorbjørn Ravn AndersenJun 29 at 14:44

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo mkdir -p /usr/lib/mozilla/plugins #just in case, this will be added to the package in the next version
sudo apt-get install oracle-jdk7-installer

The simplest way to install Java on Ubuntu is to use OpenJDK. This will work fine for most people. To install it, click on the small button with the Ubuntu logo on it, as shown in the screenshot below.

After opening the Dash Home, you need to type in Terminal. Click on the icon that is circled in the screenshot below.

This will open the Terminal, which is Ubuntu's version the the Windows Command prompt, though the Terminal has many more features. Now, copy and paste the following command into the Terminal window. You will need to use ControlShiftV to paste text into the terminal.

sudo apt-get install -y openjdk-7-jre openjdk-7-jdk

You will need to enter your password to use this command. Although it will not show up in the Terminal, it will still be entered when you type it. After running this command, you will be set up to run and develop Java applications.

Installing Oracle Java

OpenJDK works fine for most people, but if you play Minecraft, you will want to use Oracle Java instead. To install Oracle Java, run the command below one at a time in the Terminal.

-1 for 3 major reasons: 1 - JDK and JRE alone are not enough to enable java in Web Browsers. You still need icedtea-plugin package (icedtea6-plugin or icedtea7-plugin, the one that matches your java); 2 - JDK already includes the JRE, so no need to install both. Choose either JRE for regular users (like the OP) or JDK for java developers. 3 - Since you had the trouble to post nice screenshots, why suggest the terminal route? Software Center is much more friendly and recommended in this case
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MestreLionMar 19 '13 at 2:28

Thanks a lot... but i tried the last sentence "sudo update-alternatives --config java" says "There is only one alternative in link group java (providing /usr/bin/java): /usr/lib/jvm/java-7-oracle/jre/bin/java Nothing to configure." How this is supposed to check if it is in use ???
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SeptrbaMar 2 '13 at 14:35

@Septrba You have only "one" Java version installed, only one can be in use, and it's the one you have installed. If you had more than one installed, it would list and show which one is in use. Probably shouldn't have added that to my answer, since it was probably more confusing than helpful. :P
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pileofrocksMar 4 '13 at 20:39

Unfortunately, because of issues with its license, Oracle Java is no longer distributed within the official Ubuntu repositories. You have two main options: either try OpenJDK -- an open source replacement for Oracle Java -- or proceed with the "manual" installation (which is exactly what you were trying to do). Both these options are described on the help wiki: https://help.ubuntu.com/community/Java. This page also include some other alternatives that, depending on your needs, you may find more suitable.

Just a side note: most of the time, with Ubuntu, you should not download software from the Internet, but rather use the Ubuntu Software Center. The software you'll find there is ensured to be stable, safe and to respect the standard conventions of the system. Oracle Java is just an exception to this rule.

Your answer would be that the OP installs the previous Java Runtime Environment, and not the latest version jre-6u25-linux-i586.bin
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scouser73Jun 13 '11 at 14:33

1

Scouser73, jre-6u25-linux-i586.bin sounds like the proprietary Java implementation from Oracle. This question is about OpenJDK.
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LekensteynJun 13 '11 at 19:01

The one that is marked (in orange) is the open-jdk java6 runtime!
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AlvarJun 13 '11 at 19:27

scouser73 is referring to a security update of Oracle Java. I don't know if the current version if affected, the installed JRE version is 6b22 but bear in mind that this is unrelated to the version number of Oracle Java, see dbhole.wordpress.com/2011/05/27/…
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LekensteynJun 13 '11 at 19:33

well, Scouser73 had problems with a we page. I only use the jdk and that is all I ever need so I thought it would help.
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AlvarJun 13 '11 at 20:38

Install OpenJDK (The open source equivalent to Sun's Java) directly from Ubuntu Software Center. All you need to do is search for Java. That tends to work as is for me.

If you need Sun's Java, say if you want to play Minecraft, you download the JRE as you described from Java.com, but make sure your .bin-file can be executed. You do that by opening a terminal and typing the following (I will assume you have it in your Downloads folder so change the cd line accordingly if that's not where it is):

cd /home/user/Downloads
sudo chmod +x jre-6u31-linux-i586.bin

Then, you should be able to close your terminal, right click on your .bin-file and select "Execute", which should run the installer. If this is not an option, just do the following from terminal (in the same folder as the two other actions):

./jre-6u31-linux-i586.bin

That simply runs the specified file and if you successfully typed in the two first lines, the installation.

I made a text-based Java installer using terminal commands. It uses wget, tar, update-alternatives, and ln. It will install the Oracle JRE with the Firefox plugin.

You can download the installer from Google Drive here. Then put it in your home folder, open Terminal and type bash Install. Then it will run the installer in Terminal. It uses sudo, so you will need to type your password after it downloads. Also, this is the 64-bit version, so I will add the 32 bit later.